In this type of a liquid sample analyzer, as described in JP2007-17302A, there is a cartridge detachably attached to a measurement main body. This cartridge includes a flow path for flowing a diluted sample blood, which serves as a liquid sample, and a detection part provided in the flow path to measure the sample blood.
In one specific configuration, the cartridge includes: a first substrate, which forms a concave groove on the surface; a second substrate, which configures the flow path by covering an opening part of the concave groove when adhered to the first substrate and which forms a detection part, the detection part in contact with the sample blood and a lead line; and an adhesive sheet for joining the first substrate and the second substrate. Further, the adhesive sheet is configured to almost entirely cover a surface of the first substrate except for a part corresponding to a place where the detection part is formed. As the cartridge is configured in this manner, the detection part is contained and arranged in a stepwise concave portion formed by the adhesive sheet and the second substrate in the flow path (see FIG. 12).
In the cartridge, when the sample blood flows in the flow path, the sample blood experiences surface tension from a flow path wall surface (FIG. 12, at (a)). As such, the flow of sample blood is blocked at an upper-stream side corner part of the stepwise concave portion configured by the adhesive sheet and the second substrate, while the sample blood flows on an inner surface of the concave groove of the first substrate (FIG. 12, at (b)). In this manner, an air layer is formed in the vicinity of the detection part and the sample blood directly flows on the inner surface of the concave portion (FIG. 12, at (c)), and thereby causes a problem that the sample blood contacts a lower-stream side corner part of the adhesive sheet and an air bubble is formed in the vicinity of the detection part (see FIG. 12, at (d)). When the air bubble has been formed in the vicinity of the detection part as described above, there is a problem that a signal from the detection part is varied or the detection part and the liquid sample are insulated from each other, deteriorating accuracy of a measurement.
In addition to the case of forming the air bubble due to the air layer, as described above, an air bubble included in the sample blood has a tendency to stay in the stepwise concave portion formed by the adhesive sheet and the second substrate, and as a result, there is a problem that the air bubble adheres to the detection part. When the air bubble has adhered to the detection part as described above, there is a problem that a signal from the detection part is varied or the detection part and the liquid sample are insulated from each other, deteriorating accuracy of a measurement.
To address this, in general, as a method for removing the air bubble that adhered to the detection part, it can be considered to make the air bubble difficult to adhere to the detection part due to arrangement of a position of the detection part itself on a bottom surface or right and left surfaces of the flow path or in a state of being suspended in the flow path.
However, since the only force applied to the air bubble is buoyancy, there is a problem that once the air bubble attaches to the detection part, removal is difficult. In addition, in a case where the detection part is formed on the upper surface (a case of FIG. 12), there is a problem that the removal cannot be achieved by buoyancy.
As other methods for removing the bubble attached to the detection part, a method for increasing the buoyancy applied to the air bubble to remove the air bubble by decompressing inside of the flow path to enlarge a size of the air bubble or a method for stirring liquid in the vicinity of the detection part by using a stirring device such as a stirrer in the flow path may be employed.
However, in the case of the former, since a pump for decompressing inside of the flow path is separately required, and accordingly, a device configuration becomes not only complicated, but also cost is increased. Thus, this method is not preferable. Additionally, in the case of the latter, since it is required to contain the stirrer in the flow path, the configuration becomes not only complicated, but also requires an external force to drive the stirrer. Thus, there is a problem that the device configuration becomes further complicated.